You can use intervals not only with exact quantities but also with approximate numbers. Even with machine‐precision numbers, the Wolfram Language always tries to do rounding in such a way as to preserve the validity of results.

This shows explicitly the interval treated by the Wolfram Language as the machine‐precision number 0.

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This shows the corresponding interval around 100., shifted back to zero.

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The same kind of thing works with numbers of any precision.

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With ordinary machine‐precision arithmetic, this computation gives an incorrect result.

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The interval generated here, however, includes the correct value of 0.